This proposal describes the framework of an Avenir DP2 grant for Dr. Daniel Lingwood, currently an Assistant Professor at Harvard Medical School and principal investigator at the Ragon Institute of MGH, MIT & Harvard. Dr. Lingwood's research focuses on deciphering the early events of B cell antigen recognition to guide the design of antibody vaccines. Most antibody responses arise through stochastic diversification of the germline antibody repertoire, a process that can complicate vaccine efficacy because the target upon which the responding antibodies center is random. However, Dr. Lingwood has found that in some cases, viral sites of vulnerability can be non-randomly recognized through conserved elements genetically encoded within the repertoire. The result is a pre-programed anti-viral response capacity that can be `activated' by vaccination. In this application, Dr. Lingwood proposes to apply this principle to develop a vaccine that elicits broadly neutralizing antibodies (bnAbs) against HIV. Of central interest is the elicitation of VRC01-like antibodies now found in multiple individuals infected with this virus. VRC01-class antibodies neutralize ~90% of HIV stains through a remarkable converge of structure aimed at engaging the functionally conserved CD4 binding site (CD4bs) on the HIV envelope glycoprotein (Env). The CD4bs is one of the few conserved features of the HIV envelope and is a key target for vaccine design. In all cases of VRC01-class development, usage of the antibody heavy VH chain gene IGVH1-2*02 is non-random and obligate, suggesting that a genetically encoded antibody sequence predisposes for this broadly neutralizing response. To evaluate whether IGVH1-2*02 usage can be harnessed to produce HIV bnAbs in the vaccine setting, Dr. Lingwood now proposes to engineer transgenic mice that produce fully humanized IGHV1-2*02 antibody responses. These animals will then be injected with a diverse set of recombinant Env immunogens using a sequential immunization procedure that Dr. Lingwood has developed to focus the antibody response on conserved features of Env, namely the critical CD4bs. Dr. Lingwood hypothesizes that a combination of `correct' VH gene usage and immune focusing to this key site of viral vulnerability will provide a means of reproducibly eliciting bnAb responses by vaccination. Such a vaccine could: 1) offset the difficulty in maintaining life-long compliance with anti-retroviral therapy, a problem that is disproportionately high amongst individuals that engage in high risk behaviors, such as drug and substance abuse; and 2) provide an economically feasible approach to global eradication of the virus. Defining, and then harnessing, a genetic basis for bnAb elicitation aims to overcome the failure of traditional approaches to HIV vaccination and is consistent with the mission of both NIDA and broader mission of the NIH.